Receptacle of molded pulp



Patented Jan. 8, 1935 UNITED STATES PATENT OFFICE RECEPTACLE or MOLDED PULP Wis.

Application January 9, 1933, Serial No. 650,750

5 Claims.

This invention relates to improvements in receptacles'of molded pulp.

It is the primary object of the invention to provide a novel and improved receptacle having 5 relatively great strength, high resistance to the penetration of liquids and to disintegration, low thermal conductivity, smooth walls free of mold marks and pressure ridges and of substantially uniform thickness throughout except as hereinin after noted, an attractive parchment-like finish, and ribbed and grooved surfaces for ornament or utility appearing on one face only without any corresponding underlay on the opposite face of the wall of the receptacle.

The present application is a continuation in part of application 491,433, and a companion to an application executed of even date herewith entitled The art of molding pulp containers, and pertaining to a method by which a receptacle or container embodying the present invention may be made.

The drawing shows a receptacle embodying the invention, partially in side elevation and partially in vertical axial section.

The above entitled applications disclose preferred methods by which cups embodying the invention may be made. While the methods disclosed are different in certain respects, their results are similar from the standpoint of many of the annexed claims. A typical method of pro,- ducing the cup will be briefly summarized here.

A reticulated mold, internally subjected to vacuum, is inserted in a pulp bath, and the flow of liquid through the mold causes pulp to be deposited thereon to build up a blank on the surface of the mold. This blank is dried sufficiently to be self supporting. While it still retains a large portion of its free water the blank is sub-v jected to compression which is internally directed upon a supporting mandrel and is so conducted that the blank is not permitted to expand under pressure. If desired the pulp of the blank may be drawn slightly over the mandrel so as to displace a certain amount of pulp toward the'margin of the blank.

The dies used in conducting the pressure operation are preferably smooth surfaced to eliminate all marks of the mold except where ooves or ribs are desired for ornament or for the retention of a cover for the receptacle. The dies may be grooved or ribbed to produce a complementary configuration in the pulp without any underlay such as is usually required to give' an embossed effect in any molded'article. Part of the material displaced toward the margin of the cup may be used in building up such'ribs.

Upon completion of the forming operation the cup is preferably allowed to dry, and finally its margin is preferably die-cut or sheared to pro- 5 vide a smooth lip, this being particularly desirable when the receptacle comprises a cup used for drinking purposes. Simultaneously with the shearing operation, all of the marginal portions of the cup are preferably subjected to high com- 10 pression, not only to facilitate the shearing out but also to reduce these portions of the article to accurately fix dimensions to produce a uniformity of size not found in any like product heretofore.

The result of the foregoing process is shown in the drawing. 11: comprises a pulp cup, exemplifying the invention. The cup has a wall 1 of inverted frusto-conical form and of substantially uniform thickness from the ornamental go ribs 2 downwardly. ,The bottom 3 is integral with the cup and, in order that the cup may be assured of standing level on a smooth surface, the central portion 4 of the bottom is preferably pressed upwardly as shown.

It is particularly to be noted that except where ribs are desired, both the inner and outer wall surfaces of the cup are entirely smooth and free from mold marks. The pressure applied to the pulp in order to produce this result will have 30 flattened out the lumps or stucco-like irregularities found in every thick deposit of pulp, and the resulting appearance of the product will be most attractive. The drawing cannot adequately disclose the mottled or parchment-like shading of '5 the outer surface .of the cup attributable to the flattening of the pulp. The original irregularities of the pulp may be referred to for convenience as lumps, although they do not differ in substance from adjacent portions of the pulp and w are merely a form of rough surface.

There is no interior groove corresponding to the ribs or bands formed at 2 on the outside of the cup. The inner surface of the cup is preferably smooth at the point where the ribs 2 occur. a

If it is desired to make the cup useful as a closed receptacle it may be provided with an interior rib 4 forming a'shoulder' against which a cover 5 may seat. Above the interior rib 4 is a shallow channel at 6 which receives the cover 5 so with a snap action. In receptacles which are to receive disk covers such as that fragmentarily shown at 5 the accurate size of the mouth is of great importance.

In order to enable the cup to be used practi- I 8, are all effected without any deflection what-- ever of the outer surface of the cup wall, which continues smooth and unbroken from the ribs 2 to the rim 7. Thus, one of the characteristic features of the present cup lies in the fact that the wall is of varying thickness. The elasticity of the cup while wet has been utilized to permit of this irregular internal wall contour, the incomplete blank being blown from its forming mandrel or die when required to enable its ribs to clear the grooves in which they were formed.

The cup herein disclosed is preferably made from wood pulp or paper pulp. The pulp will ordinarily contain a size. If the material of the cup were to be manipulated to any great degree .while dry the rigidity derived from the presence of the size in the pulp would be destroyed and the wall of the cup would become limber or unduly flexible. It would then tend to absorb and leak liquids. In the cup as described the wall is maintained substantially rigid, and it will readily hold its form during handling when the receptacle is full of a liquid. The liquid may be of boiling temperature without destroying the cup or in any way softening it or impairing its rigidity.

Furthermore, it is possible for a person to hold in his hand a cup of this type filled with a liquid at boiling temperature without sustaining any burns, the cup being impervious to the liquid and having a high thermal insulating value.

The joint between the side wall and the bottom of the cup is uniformly compressed, bears no pressure marks, and has no line of weakness. It is equal in density to the remaining wall portions of the article.

It .will be apparent that the receptacle herein disclosed fully satisfies the objects of this invention and is useful for many purposes for which the ordinary paper or pulp receptacle is not adapted. I

I claim:

1. A uniformly tapered receptacle having an open mouth and a somewhat smaller bottom and madeof paper pulp throughout, the side and bottom walls having substantial thickness, the inner surface of the sides and bottom havingthe fibers walls havingsubstantial thickness and smooth inner and outer surfaces, the inner surface of the sides and bottom having the fibers thereof substantially unbroken and firmly pressed and compacted to such a degree as to produce a smooth hardened condition thereof constituting an interior surface film highly resistant to the penetration of aqueous liquids whereby to preserve said receptacle substantially impervious, thermally resistant and mechanically strong.

3. A tapered receptacle having an open mouth and a somewhat smaller bottom made integrally resistant and mechanically strong, the ends of the fibers composing the pulp walls of said receptacle being exposed solely at the marginal rim thereof, said rim being circumferentially sheared whereby the. receptacle is trimmed to a prede1 termined overall diameter.

4. A continuously tapered receptacle having an open mouth and a somewhat smaller bottom and made integrally of paper pulp throughout, the side and bottom walls having substantial thickness and being joined at a corner margin at least as-strong as the adjacent wall portions, the inner surface of the sides and bottom having the fibers thereof firmly pressed and compacted to such a degree as to produce a smooth hardened condition thereof constituting an interior surface film highly resistant to the penetration of aqueous liquids whereby to be firmly insulating and substantially impervious independently of extraneous waterproofing.

5. A continuously tapered receptacle having a mouth and a somewhat smaller bottom and made unitarily of paper pulp throughout, the side and bottom walls having substantial thickness and having smooth interior and exterior surfaces, the irmer surface of the sides and bottom having the fibers thereof firmly pressed and compacted to such a degree as to produce a smooth. hardened condition thereof constituting an interior surface film highly resistant to the penetration of liquids whereby said receptacle is substantially impervious to such liquids independently of extraneous coating, the wall portions of said receptacle' varying in thickness according to a predetermined pattern whereby the effect of embossstantial change of density.

' ANDREW KEIDING.

'ing is secured without underlay and without sub- 

